Production of finely-divided metallic materials



Dec. l0, 1929.

J. H. WHITE PRODUCTION OF FINELY DIVIDB'D METALLIC MATERIALS Filed Jan'. 3l, 1929 A TTORNEV Patented Dec. i0, 1929 JOHN' E. WHITE, OF CRANFORD,

TOBIES, INCORPORATED, F NEW YORK, N.

NEW JERSEY, ASSIGNOR T0 BELL TELEPHONE LABORA- Y., A CORPORATION OF NEW YORK PRODUCTION 0F FINELY-DIVIDED METALLIC MATERIALS Application led January 31, 1929.l Serial No. 336,481.

' ods of producing such materials.

An object of the invention is to facilitate the production of finely divided metallic material, such asfinely divided magnetic material for use in loading coil cores and the like.

Another and more specific object is to embrittle a magnetic material, such as an alloy containing nickel and iron, so that without deleteriously aecting its electrical and magnetic characteristics, the material may be readily reduced to finely divided form suitable for use in magnetic cores for loading coils and the like.

The invention is of advantage in the productiontof magnet cores, particularly loading coil cores of the so-called dust type comprising finely divided magnetic material and insulation, such, as are described in the U. S. patent to Elmen 1,297,126, issued March'll, 1919. In the manufacture of such magnetic cores,it is the usual practiceto subject the magnetic material in solid form to mechanical processes, such as hot rolling, grinding, crushing and sieving, in order to reduce the material to a suitably finely divided state. Where especially good magnetic characteristicsare required in such cores, alloys comprising nickel and iron alone or in combination with other metals are often used as the magnetic materials. Such alloys are sometimes very tough and therefore are not easily converted into finely divided form by the usual mechanical processes. It is usual therefore before subjecting these magnetic alloys to such mechanical processesto add some additional material thereto which will notimpair the magnetic characteristics of the alloy, but will serve to embrittle it, so that it may be readily reduced to finely divided form by mechanical processes. i

In accordance with the invention, ya tough metallic material-is embrittled to a desired degree by incorporating therein a small amount of sulphur in such manner that the sulphur is distributed more yor less uniformly throughout the material. It has been found that a very small amount of sulphur incorporated in a magnetic alloy, for example, a nickel-iron alloy, will, without impairing appreciably the electrical or magnetic properties thereof, sufficiently embrittle the alloy so that it may be easily reduced to finely divided form. The incorporated sulphur may be in any desired form but is preferably in the form of a sulphide of one of the magnetic materials forming the alloy, for instance, iron sulphide or nickel sulphide.

The exact nature of the invention will be understood from the following detailed description thereof when read in connection with the accompanying drawing, the single figure of which shows schematically an application of the invention to the production of finely divided magnetic material.

The invention will be described as applied to the production of finely divided magnetic material. As indicated in the drawing, the

magnetic material is first melted. This may be conveniently done by placing the solid material in a suitable container and subjecting it to heat in a suitable furnace until the material is reduced to molten form. A small quantity of sulphur or a sulphur compound, preferably a sulphide of one of the constltuents of the magnetic material, is then added to the molten magnetic material and mixed thoroughly therewith. After the sulphur or sulphur compound has been thoroughly distributed throughout the molten material, the resulting product is poured into an ingot mold, and as soon the mold is removed and the ingot allowed to cool. The ingot obtained in this way is of extremely brittle crystalline structure, and therefore may be easily reduced to. finely divided form by subsequent mechanical operations such as crushing, rolling and sieving.

The fineness of the dust particles obtained by the above described process will depend uponthe sizeof thecrystals in the ingot. If it is desired to obtain veryfine dust, it is usually necessary to subject the ingot to certain treatment prior to breaking it up, to produce va fine grained struct-ure therein. One method for accomplishing this` which is described in the U. S. patent' to Beath et al.,.1,669,649 issuedMay 15, 1928, consists in successively as the material is solidified finely divided magnetic particles passing the hot ingots or billets of magnetic material received from the heating furnace through progressively reducing rolls until they have been greatly reduced in' cross-section. This mechanical Working of the metall breaks down the crystalline struct-ure of the billet and produces A'a very fine grained crystalline structure therein. If asmall amount of sulphur has been previously incorporated in the magnetic material of the ingot in the manner described above, fracture of the matcrial in the subsequent crushing will take place principally along the crystal boundaries, probably due to the incorporated sulphur being collected between the crystals of the material. This will result in the yield of a large percentage of dust particles Which are small enough to pass through a 120 mesh sieve, and which are particularly suitable for continuous or lump loading of signaling circuits.

The method of the invention as described above is applicableto metallic materials in general, but Ait isofpparticular,advantage in connect-ionfjwith the reduction to finely dividedform of tough metallic materials, such as magnetic alloys including nickel and iron.

The amount of sulphur or sulphur compounds necessary to be added to embrittle the particular material will depend upon the nature of the elements constituting the mate-1 rial and their degree of purity. In a particu-y lar case in which the material to be reduced to finely divided form comprised a magnetic alloy. of high grade commercial nickel and` -iron 1n the ratio of about 781/2per cent nickel to 21% per cent iron, which alloy contained some sulphur as an impurity, it was found that the addition of iron sulphide in the proportions of 0.02 per cent by weight of the alloy did not impair the magnetic characteristics of the material and made the allo sufliciently brittle. When the materials to e em. brittled do not contain sulphur or other embrittling .material as impurities, it will be necessary toadd a larger amount of the sulphur or sulphurcompound for embrittling the material.` y

Magnetic dust made in accordance with the method 'of the invention isparticularly adapted for use in magnetic rings or cores for loading coils which may be constructed in a manner similarl to that described in the U. S. patent to Andrews et al., 1,669,645, issued May 15; 1928. The essential steps in `the method of producing such cores or rings described in that patent consistedin first an-` nealing the magnetic particles, coating the with a s uitable insulating material, 'and A then forming the coated particles into rings or cores by the application of h'iglt pressure thereto, the resulting rings or cores being givenasubsef uent annealing heat treatmentto improve t eir magnetic characteristics. Aplurality of rings .,thus formed are then stacked coaxially to form a core, on which is mounted the usual toroidal winding, the number of rings useddepending. upon the existing electrical characteristics of the circuit with which the loading coils are to be associated.

`To enable a clearer understanding of the l 1. The method of reducing a tough metallicl Y material to iinely divided form, which consists in incorporating in said material a small quantity of sulphur to embrittle it, and then mechanically breaking up the resulting product to the desired degree of fineness.

2. The method of reducing a tough metal'- lic, material to -finely divided form, which 'fjconrsistsin alloying said material with a small of sulphur to embrittle it, treating t e embrittled alloy to produce a line-grained crystalline structure therein, and then breaking up the resulting product.

3. The method of reducing an alloy of metals which is ordinarily quite tough to a finely divided form which consists in incorporating in saidalloy of metals a small quantity of sulphur to embrittle it, treating the embrittled alloy -to roduce a fine-grained crystalline structure t erein, and then break- Aing up the resulting product to the desired degree of ineness.

4. The method of. reducing a magnetic material containing nickel and iron to a finely divided form which consists in alloying-the magnetic material -with a .small quantity of sulphur to embrittle it,treating theembrittled alloy to produce a fine-grained crystalline structure'therlein, and breakin up ,the resultingproduct to the' desired dgree of ineness. 5. The method ,of core .material for in 'reducing finely divided uction coils from magnetic material containing nickel Vand iron,

whichconsists in reducing said magnetic material tol the molten st-ate, distributing throughout the molten material a small' quantity of a sulphide o' one of the constituents of said magnetic material to embrittle said material, treating the resulting compound to produce a' fine-grained crystalline structure therein, and breaking up the resulting" product to the desired degree of fin'eness.

In witnessvwhereof, I hereunto subscribe my name this 30th day of January, 1929.

- .JOHN H. WHITE. 

